If You Ever Cheat On Me
by beccalovesmerder
Summary: A MerDer one-shot inspired by the 8x18 promo for The Lion Sleeps Tonight and Meredith's warning to Derek. Enjoy!


**Hello!**

**I know I should be updating my other two fics, but, as with my other two one-shots, I got an idea in my head and I couldn't write anything else until this was done.**

**This is inspired solely on the promo for 8x18, **_**The Lion Sleeps Tonight,**_** and Meredith's warning to Derek, "If you ever cheat on me, I'll kill you". **

**I doubt this is what the show is going to do, but it was a fun, little exercise for me :)**

**Hope you all get a kick out of it too!**

**Enjoy!**

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><p><strong><em>If You Ever Cheat On Me<em>**

'_Why do people cheat?'_

Meredith remembered asking those words years ago, but, sitting here now, she felt no closer to knowing the answer.

Cristina was sprawled out on her couch, finally sleeping. Her face was flushed and her eyes and nose were raw from crying. No doubt they'd be puffy and swollen when she woke up.

Meredith shook her head sadly as an exhausted sigh escaped her body. It had been a long night.

Actually, that was an understatement. Last night had been one of the longest nights of her life.

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><p>After yelling at Lexie for the complications in Laurie's surgery, Derek had paged Meredith letting her know that he had picked up Zola from daycare and they were going home. She still had four hours left on her shift and she had a feeling they'd be the longest of her life.<p>

When she finally got home, the house was silent. It was late enough that Zola should be sleeping in her crib and, if she had to guess, Derek was probably brooding in their bedroom. She had been dreading this moment the entire drive home. Derek mad was never fun. Derek mad at her was just plain horrible.

She had gone up there expecting a fight, but instead he didn't seem to want to speak at all.

But when he, in not so many words, told her he didn't want her to leave, the tense finally left her shoulders and a tears threatened to spill over her eyelids in relief.

Meredith had naively thought her horrible evening was going to end there. She was lying peacefully beside her husband and his warm hand hadn't released hers in all the time they were laying there. Eventually they would have to talk, but for now, it was as perfect as it was going to get.

She was half asleep when Cristina had started pounding on the door.

She was hysterical and sobbing. Meredith almost couldn't make out her words due to lack of sleep and Cristina's sobs, but eventually she figured it out.

Owen slept with another woman. Owen cheated on her.

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><p>She'd had all night to process the information, but Meredith was still in shock. She couldn't imagine how Cristina was feeling. It wasn't even her husband and she felt like she could throw up.<p>

A soft creek from the stairs made Meredith shift her focus from her exhausted friend as she watched her husband descend quietly. She rose to meet him in the hallway to allow Cristina a few more moments of quiet sleep.

"Is Zola still sleeping?" she asked quietly, indicating to the baby monitor Derek had brought down with him.

"Yeah, she's still out like a light. I checked on her before I came down. I figured we have awhile before we have to go in. She can sleep a little longer."

"Yeah," Meredith agreed.

"How is she? Is she alright?" Derek asked in a hushed voice, as not to disturb their sleeping guest.

"No," she responded in an angry whisper. "No, Derek. She is not alright. Her husband slept with someone else. Her marriage is crumbling around her. The last thing she is is alright."

Storming past Derek, she made a beeline for the kitchen door, but he was hot on her heels.

"Mer, I didn't mean to upset you. I was just-"

He was cut off when she unexpectedly stopped in the doorway and whipped around to face him.

"If you ever cheat on me," she said in a serious voice, "I'll kill you."

Just as quickly as she had turned to him, she twisted back around and strode purposefully over to the coffee maker.

"Wait, what?" It was too early for this in his opinion. "Why would you think I would cheat on you?" he questioned, genuinely confused. "You think I would do that to you?"

"What's stopping you?" she muttered, fighting with the stubborn appliance to get the coffee started.

"What's stopping me?" Derek repeated incredulously. "Meredith, where is this coming from? I would never cheat on you."

"How do you know that?" Meredith exclaimed, giving up on the coffee maker and finally looking at him. "How do you know? Don't you think Owen thought that when they stood in our living room, saying their vows? Don't you think Addison thought that when you married her? And Richard? The truth is anyone can cheat."

"Meredith-"

"You cheated." Meredith interrupted again. It wasn't an accusation. She said it as if she were stating a simple fact.

"I know Addison cheated on you first, but you were still married the night we met at Joe's. And the two months before she showed up. I know I wasn't revenge or a way to get back at her for hurting you, I know that. But-"

"I fell in love with you." Derek was the one to interrupt this time.

Meredith offered him a smile, but it didn't reach her eyes. "You fell in love with me," she nodded. "But you still cheated. I may appreciate your reason, but I'm sure Addison didn't. Hell, Addison had her reasons for sleeping with Mark, but did that make it any better for you?"

Finding himself without an argument, Derek remained silent.

"And I mean, crap! I've been on both ends," she groaned, throwing her hands up in frustration. "I don't blame myself for first two months of our relationship because if I had known you were married, I never would have slept with you in the first place. But that night in the exam room, at the prom?" She paused momentarily to make sure he remembered.

'_Like I could possibly forget,'_ Derek internally snorted.

"That night I knew exactly what I was doing. I knew you belonged to someone else. I knew you were married. But when you grabbed me and kissed me, it was the first time I felt like I could finally breathe in six months so I didn't care about any of that other stuff. I needed you so badly that night and I think you needed me too." Her eyes were so pained and her voice quivered with emotion. All Derek wanted to do was take her in his arms and make her forget that pain had ever existed.

"But that doesn't make what we did any more right. You had a wife and I had a boyfriend. We hadn't actually decided that we were exclusive so maybe technically I didn't cheat on Finn, but he still didn't deserve that. And Addison didn't deserve to find my panties in your coat pocket."

"I regret hurting Addison, but I don't regret being with you."

"But we cheated, Derek! This is exactly my point! I never thought I could do that, but I have!"

"It was a horrible time, Meredith. Both of us were miserable; both of us missed the other. But we made it right in the end."

"That doesn't make it better! It doesn't make it- Uhhhg," Meredith cut herself off with an aggravated groan and rubbed furiously at her throbbing temples. "I'm getting off topic here. It's just…." She sighed heavily again, not knowing how to continue.

"Mer, why is this upsetting you so much? I know she's your best friend, but you're acting like you just expect me to cheat on you now or something. We've both made mistakes in the past. I'm not denying that. But we finally got it right. Why would I do something to mess that up?"

"All I've seen is that people cheat and that people leave," she answered sadly. "A lot of people in my life have chosen someone else of something else over me. My dad didn't think I was worth sticking around for so he made a new family. My mom chose her career. Even you when you chose Addison. And, no, before you whine about 'not this fight again', I'm not bringing it up to fight. I'm simply stating a fact. And it took me a long time and some therapy, but I like to think I've gotten past most of my abandonment and trust issues. But damn it, Derek, do you know how hard it is keep believing people I love aren't just going to up and leave when it's happening all around me? I'm not special. It happened to Cristina and to a lot of other people we know, so what the hell is keeping all this crap from happening to us?"

Derek crossed to kitchen to stand in front of Meredith. Cradling her face between his warm hands, he forced her to meet his gaze.

"Meredith," he began, making sure he had her full attention. "Don't do this to yourself. We have our moments and we've both had to forgive each other for a lot. But like I said, I truly believe we've finally got it right. We're good, Mer. We're really good." His eyes were intense and she wanted more than anything to believe him. If only that nagging voice of doubt would shut-up.

"And as for what's going to keep us from cheating on each other, I've never once worried about that with you. And there is nothing in this world that would make me cheat on you. I can't even think about it. We're not going to hurt each other like that because we love each other and we know we have something worth fighting for. We have daughter together. You and Zola are the most important things in my life. So why would I do something to screw that up?"

"I don't know," Meredith managed to mumble in response. The conviction in his tone and the sincerity in his eyes made a very convincing argument. She suddenly felt very stupid for her earlier outbursts.

Derek tilted his head and offered her a loving smile. His thumb gently wiped the skin under her eye to rid her face of an escaping tear before moving his hands down to her shoulders.

"In fact, I'm so confident that this will never be an issue we'll have to deal with, that I give you full permission to kill me should I ever completely lose my mind and cheat on you."

Meredith raised an amused eyebrow in response. "I'll hold you to that, you know," she warned, only half teasing.

"I should hope so," Derek teased back before pulling her into a tight hug.

"Sorry I kind of yelled at you." Meredith's apology was slightly muffled by Derek's shoulder as she pulled herself closer and melted into his embrace. She hadn't been this relaxed in what felt like forever and she never wanted to leave.

"It's okay," he whispered back as he swayed them gently back and forth. "Nothing about this situation is easy and I know you've been up all night with Cristina."

"Still," she reasoned. "That couldn't have been what you were expecting when you came downstairs."

"True," he almost chuckled. "But we still have over an hour before we have to leave for the hospital," he trailed off suggestively.

"And?" She pulled her face away from his shoulder and gave him a knowing grin.

"I may have a few ideas about how you can make it up to me," Derek purred, his lips hovering over hers as he pressed his forehead against his wife's.

Before Meredith could come up with a witty retort, a piercing cry sounded from the baby monitor Derek had placed on the table. Sighing with disappointment, the couple held on to their fleeting moment a second longer before stepping out of the hug.

"Rain check?" Meredith offered hopefully.

"Definitely."

Another cry ripped through the monitor, reminding the parents that their baby had no plans to be ignored this morning.

"Your daughter is crying," Meredith informed him cheekily.

"She's _my_ daughter now?" her husband laughed.

"Well, Cristina needs to be woken up if she wants to get to work on time. Would you rather do that?"

"Coming, Zo!" Derek called out with mock fear.

"A wise choice," Meredith agreed.

Before he completely left the kitchen, Derek hesitated in the doorway. "Are you okay now? I mean, I know you're not because your friend is hurting, but are we okay?"

"We're okay," she nodded with a soft grin.

A beautiful smile stretched across Derek's face, only making Meredith happier. She always wanted to be the reason for that smile.

"We're okay."

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><p><strong>Thanks for reading!<strong>

**Reviews are always appreciated! Let me know what you think!**


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